JP2003105318A - Heavy metal-fixing agent and method of stabilization for the heavy metal-fixing agent at low temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heavy metal-fixing agent having low temperature stability such as keeping stable state at a cold district by lowering coagulation point of the heavy metal-fixing agent including a diethyldithiocarbamate in high concentration and to provide a method of stabilizing the agent at low temperature. SOLUTION: This heavy metal-fixing agent including aqueous solution of a diethyldithiocarbamate as a principal ingredient includes 0.1-5.0 wt.% of one or more kind of compounds selected from piperazine and a polyamine. The heavy metal-fixing agent including 50-60 wt.% of the diethyldithiocarbamate does not coagulate at -9 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to incineration ash generated in an incinerator plant for industrial wastewater, industrial waste, and municipal waste, and fly ash and heavy metals discharged together with exhaust gas from an incinerator plant and the like in an electric dust collector. A heavy metal fixing agent that fixes heavy metals contained in contaminated soil, etc. and prevents them from being dispersed and released into the environment, and a method for stabilizing them at low temperatures, and in particular, to efficiently treat incinerated ash containing heavy metals even in cold regions. The present invention relates to a heavy metal fixing agent and a method for stabilizing the same at low temperature.

[0002]

2. Description of the Related Art Wastewater from factories, incineration ash discharged from an incinerator plant such as municipal waste and industrial waste, fly ash collected from electric dust collectors from smoke exhaust, and heavy metal contaminated soil are treated. In this case, incineration ash, in order to eliminate the release of harmful heavy metals such as lead, chromium, cadmium, arsenic, and selenium contained in fly ash to the environment, a method of solidifying the incineration ash, fly ash, etc. by cement, Although there was a method of extracting heavy metals by treating incineration ash, fly ash, etc. with an acid, there were problems of increasing the volume of waste and treating heavy metals extracted with an acid. For this reason, a treatment with a heavy metal fixing agent has been adopted, which does not require a special device and does not require post-treatment. As a heavy metal fixative,
Liquid chelating agents of amine derivatives having a dithiocarboxy group as a functional group are widely used because they have a high heavy metal trapping effect and can be eluted into rainwater and the like, and particularly have a dithiocarboxy group as a functional group. An aqueous solution containing diethyldithiocarbamate as an amine derivative has been preferably used.

The aqueous solution containing diethyldithiocarbamate used as such a heavy metal fixing agent is mixed with diethylamine and an alkaline aqueous solution of sodium hydroxide, potassium hydroxide or the like under a nitrogen atmosphere and the temperature is in the range of 5 to 30 ° C. It was produced as an aqueous solution containing a high concentration of diethyldithiocarbamate by reacting with dropwise addition of carbon disulfide with stirring. However,
The heavy metal fixing agent comprising an aqueous solution containing diethyldithiocarbamate produced by the above method has a high freezing point at a high concentration of diethyldithiocarbamate, for example, 50% by weight or more, and a low temperature of -7 ° C or lower. When used in cold regions, etc., the aqueous solution itself solidifies, so special equipment is required for storage and storage, which also restricts work using this and not only increases cost, There were problems such as complicated labor, and handling was extremely difficult. On the other hand, there has been proposed a heavy metal fixing agent which does not crystallize at low temperature by applying an aqueous solution containing 30% by weight or more of potassium salt of diethyldithiocarbamic acid (JP-A-8-332475). It is not possible to lower the freezing point of a heavy metal fixing agent whose main component is an aqueous solution containing 50% by weight or more of a high-purity potassium salt of diethyldithiocarbamic acid, which does not contain thiocarbonate as a by-product in the potassium salt formation reaction. It was

[0004]

An object of the present invention is to lower the freezing point and to fix a heavy metal fixing agent having low temperature stability capable of maintaining a stable state without solidifying even in cold regions and incinerated ash in cold regions. An object of the present invention is to provide a method for stabilizing a heavy metal fixing agent at low temperature, which facilitates treatment.

[0005]

[Means for Solving the Problems] As a result of extensive studies to solve the above problems, 0.1 to 5.0% by weight of piperazine or polyamine was added to a heavy metal fixing agent composed of an aqueous solution containing diethyldithiocarbamate. By including it, the freezing point can be lowered, and a heavy metal fixing agent which does not solidify at a low temperature of -7 ° C or lower, particularly at a low temperature of -9 ° C can be obtained, and the heavy metal fixing agent can be stabilized at a low temperature. They have found what they can do and have completed the present invention.

That is, the present invention relates to a heavy metal fixing agent comprising an aqueous solution containing diethyldithiocarbamate as a main component, containing 0.1 to 5.0% by weight of at least one selected from the group consisting of piperazine and polyamine. ,
Regarding a heavy metal fixing agent characterized by not coagulating at a low temperature, preferably diethyldithiocarbamate is 50
The heavy metal fixing agent according to claim 1 (claim 2), characterized in that it is contained in an amount of not less than 60% by weight and not more than 60% by weight, and it does not solidify at -9 ° C. A heavy metal fixative (claim 3).

In the present invention, 0.1 to 5.0% by weight of at least one selected from the group consisting of piperazine and polyamine is added to a heavy metal fixing agent whose main component is an aqueous solution containing diethyldithiocarbamate. A method for stabilizing a heavy metal fixing agent at low temperature, which comprises:
With respect to the above, preferably, the method for stabilizing a heavy metal fixing agent at low temperature according to claim 4 (claim 5) or coagulating at -9 ° C is characterized by containing 50% by weight or more and 60% by weight or less of diethyldithiocarbamate. The present invention relates to a method for stabilizing a heavy metal fixing agent at low temperature according to claim 4 or claim 5 (claim 6).

The diethyldithiocarbamate salt used in the heavy metal fixing agent of the present invention is a salt of diethyldithiocarbamate and an alkali metal such as potassium, sodium or lithium, which is mixed with heavy metal-containing incineration ash or the like. By replacing the alkali metal with a heavy metal atom,
A chelate complex with a heavy metal atom is easily formed, the heavy metal atom is fixed quickly and strongly, and the fixed heavy metal atom is not released by rainwater or the like. The heavy metal fixing agent of the present invention is an alkali salt of diethyldithiocarbamic acid, which is a product obtained by mixing diethylamine, an alkali metal hydroxide and carbon disulfide in an aqueous solution in the production of diethyldithiocarbamate as a main component. The aqueous solution of can be applied as it is. Unreacted carbon disulfide and diethylamine are preferably removed from the aqueous reaction product solution, and unreacted carbon disulfide is removed. When carbon becomes acidic, it is possible to prevent carbon disulfide from being released.

The content of the above-mentioned diethyldithiocarbamate is not particularly limited, but is in a range such that the heavy metal can be reliably fixed even when the heavy metal is contained in a large amount in the object to be treated. Is appropriately selected, for example, in the range of 50% by weight to 60% by weight. Within this range, it binds to the heavy metal contained in the object to be treated,
It can fix heavy metals with high precision and make them insoluble.
If it is less than 50% by weight, the heavy metal may not be fixed quickly and sufficiently in the object to be treated containing a large amount of heavy metal, and if it exceeds 60% by weight, diethyldithiocarbamate is wasted. Is likely to be done.

The piperazine used in the present invention is used by being dissolved in an aqueous solution containing diethyldithiocarbamate, and either piperazine anhydrous or piperazine hexahydrate can be applied. The piperazine anhydride or piperazine hexahydrate may be used in the solid state or added to the heavy metal fixing agent as an aqueous solution, and the piperazine hexahydrate having a low melting point may be melted to be a liquid heavy metal fixing agent. It may be added to and used. The aqueous solutions of these piperazines are basic, and have the effects of lowering the freezing point of the heavy metal fixing agent and suppressing the generation of carbon disulfide generated when the aqueous solution becomes acidic due to the dissolution of carbon dioxide in the air. .

The polyamine used in the present invention is used by being dissolved in an aqueous solution containing diethyldithiocarbamate and, like the piperazine, is easily soluble in water and the aqueous solution is basic. It has the effects of lowering the freezing point of the heavy metal fixing agent and suppressing the generation of carbon disulfide generated when the aqueous solution becomes acidic due to the dissolution of carbon dioxide in the air. The polyamine is not particularly limited as long as it has a plurality of amino groups, and the amino group may be a primary amino group, a secondary amino group, or a tertiary amino group. Well, as the polyamine, those having a plurality of amino groups such as diamine, triamine and tetramine can be mentioned, but aliphatic amines are preferable, and aliphatic amines can be used as aliphatic unsaturated amines and alicyclic compounds. Amine and the like can also be applied.

As the above polyamine, a polyvalent amine having at least one secondary amino group in the molecule is preferable, and specifically, N-methylethylenediamine, N-ethylethylenediamine and N-butylethylenediamine are preferable. ,
N, N'-dimethylethylenediamine, N, N'-diethylethylenediamine, N-methyl-1,3-propanediamine, N, N'-dimethyl-1,3-propanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepenta Amine, pentaethylenehexamine, iminobispropylamine, polyethyleneimine, N- (2-aminoethyl) -1,3-propanediamine, N, N'-bis (3-aminopropyl) ethylenediamine, 3,3'-iminobis (N, N′-dimethylpropylamine) and the like can be exemplified.

The content of the piperazine is within a range in which the heavy metal fixing agent itself does not crystallize when used in a cold region, and the optimum content range is 0 with respect to an aqueous solution containing diethyldithiocarbamate. From 1% by weight to 5.
It can be 0% by weight. If it is less than 0.1% by weight, a sufficient effect of lowering the freezing point cannot be obtained. Also, 5.
The effect can be recognized even when the amount added is 0% by weight or more, but when the amount added exceeds 5.0% by weight,
Considering the effects obtained, it is preferably 5.0% by weight or less.

The content of the above polyamine is within a range in which the heavy metal fixing agent itself does not crystallize when used in cold regions, and the optimum content range is 0 with respect to an aqueous solution containing diethyldithiocarbamate. From 1% by weight to 5.
It can be 0% by weight. If it is less than 0.1% by weight, a sufficient effect of lowering the freezing point cannot be obtained. Also, 5.
The effect is recognized even when the amount added is 0% by weight or more, but when considering the amount of diethyldithiocarbamic acid used and the effect obtained when the amount added exceeds 5.0% by weight, 5.0% by weight or less Is preferred.

The above-mentioned piperazine and polyamine may be used alone or in combination with one or two of the polyamines.
One or more may be used, or one or more polyamines may be used together with piperazine.

The heavy metal fixing agent of the present invention may contain a pH adjusting agent for keeping the aqueous solution basic, in addition to the polyamine and piperazine. For those containing a pH adjuster, the hydrogen ion concentration during storage should be kept within a specified range to prevent the generation of carbon disulfide and hydrogen sulfide generated from thiocarbonate, which is a side reaction product. You can When the hydrogen ion concentration of the aqueous solution is 10 or more, even if the aqueous solution becomes acidic due to the inclusion of carbon dioxide in the air, or is exposed to high temperatures, the diethyldithiocarbamate is decomposed and disulfide is dissolved. It is possible to prevent the generation of carbon, and to suppress the generation of carbon disulfide and hydrogen sulfide due to decomposition even if the thiocarbonate as a by-product is present in the aqueous solution. Further, it is possible to prevent the generation of carbon disulfide even during the fixing treatment of heavy metals. As the pH adjuster, an alkali such as potassium hydroxide, sodium hydroxide or lithium hydroxide can be applied, and the same alkali metal hydroxide as the alkali metal hydroxide used for the formation of diethyldithiocarbamate described later can be used. Hydroxide can also be preferably used, and the addition amount thereof can be 0.01 to 200 mol% of diethyldithiocarbamate.

Further, the heavy metal fixing agent is another substance, for example,
It may contain an alkali for adjusting the hydrogen ion concentration, an acid, an antioxidant, or a water-soluble organic solvent such as methanol or ethanol.

In the method for producing a heavy metal fixing agent of the present invention, solid piperazine or polyamine is directly added after the production of an aqueous solution containing a usual diethyldithiocarbamate.
Alternatively, it may be added in the form of an aqueous solution, or the low melting point piperazine hexahydrate may be melted and added as a liquid.

The above-mentioned aqueous solution containing diethyldithiocarbamate can be produced by mixing diethylamine, an alkali metal hydroxide and carbon disulfide in an aqueous solution, but preferably diethylamine and an alkali metal hydroxide. It can be carried out by dissolving the product in water and adding carbon disulfide dropwise thereto, and it is preferably carried out in a nitrogen atmosphere. Further, it is preferably carried out at a temperature of 30 ° C. or lower, and particularly when carried out in the range of 0 ° C. to 15 ° C., carbon disulfide is generated during the treatment of the object to be treated with the heavy metal fixing agent or during the storage period. The formation of a side reaction product of the source thiocarbonate is suppressed, and diethyldithiocarbamate is selectively produced, which is preferable. The above reaction is preferably carried out at a pH adjusted to 10 or higher.

The end point of the reaction is determined by confirming by NMR or the like with the time when the particles of carbon disulfide dispersed in the aqueous solution disappear as a guide. Furthermore, in order to remove unreacted carbon disulfide or diethylamine from the aqueous solution after completion of the reaction,
Bubbling with nitrogen is desirable. Unreacted carbon disulfide and the like are separated from the aqueous solution due to heating of the heavy metal fixing agent, fluctuations in the hydrogen ion concentration, and the like, so it is desirable to remove it from the beginning.

After completion of the reaction, it is preferable to store the aqueous solution at a pH of 10 or more because the generation of carbon disulfide can be suppressed during the storage period. To store the aqueous solution of the reaction product at pH 10 or higher, 0.01 to 200 mol% of a metal hydroxide can be added to the produced diethyldithiocarbamate.

The method for stabilizing a heavy metal fixing agent at low temperature according to the present invention comprises at least one selected from the group consisting of piperazine and polyamine in a heavy metal fixing agent whose main component is an aqueous solution containing diethyldithiocarbamate. ~
It is not particularly limited as long as it is added by 5.0% by weight, and preferably 50% by weight or more and 60% by weight or less of diethyldithiocarbamate is added. Therefore, at low temperature, for example, − The heavy metal fixing agent does not solidify at 9 ° C. and can be maintained in a liquid state, and the heavy metal fixing agent can be stabilized at a low temperature.

The method of treating incineration ash or the like using the heavy metal fixing agent of the present invention may be carried out by mixing the heavy metal fixing agent with incinerator ash, fly ash, drainage or heavy metal-containing soil at a low temperature, For example, even at -7 ° C or lower, particularly at -9 ° C, the heavy metal fixing agent is a liquid without coagulation, and the contained diethyldithiocarbamate does not crystallize,
It can be treated in the same manner as the treatment at room temperature. That is, by mixing the heavy metal fixative with the object to be treated, the diethyldithiocarbamic acid contained in the heavy metal fixative binds with the heavy metal contained in the object to form a chelate complex of the heavy metal, and the heavy metal is highly accurate. It is fixed to and is insolubilized.

The amount of the heavy metal fixing agent used depends on the amount of the heavy metal contained in the objects to be treated, but in the case of incineration ash of a municipal waste incinerator, flue gas, etc.
About 5% by weight can be used. Further, depending on the form of the object to be treated or the content of the heavy metal, water can be appropriately added to the heavy metal fixing agent for use.

The object to be treated with such a heavy metal fixing agent is not particularly limited, and any substance containing a heavy metal can be applied. Factory effluent, industrial waste, incineration ash generated in the incineration plant of municipal waste, EP ash discharged with exhaust gas from the incineration plant and collected by an electric dust collector, fly ash such as ash collected by a bag filter,
Heavy metal contaminated soil, etc. are included, and the heavy metal contained in these is treated as an inorganic compound or an organic compound, and the heavy metal contained in the object is easily fixed by the heavy metal fixing agent. To be done.

[0026]

The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples. Example 1 Yellow-green without thiocarbonate added with 0.3% by weight, 0.5% by weight, 1.0% by weight, 2.0% by weight and 5.0% by weight of piperazine (UV visible at a wavelength of 500 nm. 56% by weight of the absorbance of the light absorption spectrum is less than 0.05)
A heavy metal fixing agent composed of an aqueous solution of potassium diethyldithiocarbamate was prepared. The freezing points of these heavy metal fixatives were measured. The results are shown in Table 1 and FIG. Comparative Example 1 No addition of piperazine and addition of 10.0% by weight of 56
As a result of measuring the freezing point of a heavy metal fixing agent composed of an aqueous solution containing potassium diethyldithiocarbamate by weight,
They were -7.2 degreeC and 3.5 degreeC, respectively. The results are shown in Table 1 and FIG.

[0027]

[Table 1]

Example 2 A heavy metal fixing agent comprising an aqueous potassium diethyldithiocarbamate solution containing 0.3% by weight, 0.5% by weight, 1.0% by weight and 5.0% by weight of tetraethylenepentamine was prepared. The freezing points of these heavy metal fixatives were measured.
The results are shown in Table 2 and FIG.

[0029]

[Table 2]

As is clear from the results, 0.1 to 5.0% by weight of piperazine was added, and polyamine was added to 0.1% by weight.
It was found that the freezing point of the heavy metal fixing agent comprising a 56% by weight potassium diethyldithiocarbamate aqueous solution added with 1 to 5.0% by weight was lower than the freezing point of the heavy metal fixing agent without addition of piperazine.

[0031]

EFFECTS OF THE INVENTION The heavy metal fixing agent of the present invention has a low temperature stability due to a decrease in the coagulation of the heavy metal fixing agent due to the addition of piperazine or polyamine, so that it can be retained and stored even in low temperatures such as cold regions. This facilitates the treatment of the object to be treated containing the heavy metal in cold regions, and thus can be performed inexpensively and easily.

[Brief description of drawings]

FIG. 1 is a view showing a freezing point of a heavy metal fixing agent of the present invention due to addition of piperazine.

FIG. 2 is a diagram showing the freezing point of the heavy metal fixing agent of the present invention when tetraethylenepentamine is added.

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Claims (6)

[Claims] 1. A heavy metal fixing agent comprising an aqueous solution containing diethyldithiocarbamate as a main component, containing 0.1 to 5.0% by weight of at least one selected from the group consisting of piperazine and polyamine, and at a low temperature. A heavy metal fixative characterized by not solidifying. 2. Diethyldithiocarbamate is added to 50
The heavy metal fixing agent according to claim 1, wherein the heavy metal fixing agent is contained in an amount of not less than 60% by weight. 3. The heavy metal fixing agent according to claim 1, which does not solidify at −9 ° C. 4. A heavy metal fixing agent comprising an aqueous solution containing diethyldithiocarbamate as a main component, to which 0.1 to 5.0% by weight of at least one selected from the group consisting of piperazine and polyamine is added. Method for stabilizing a heavy metal fixing agent at low temperature. 5. Diethyldithiocarbamate is added to 50
5. The method for stabilizing a heavy metal fixing agent at a low temperature according to claim 4, wherein the content of the heavy metal fixing agent is at least 60% by weight. 6. The method for stabilizing a heavy metal fixing agent at low temperature according to claim 4, wherein the method does not solidify at −9 ° C.